Local immigration office and pay for the extension, it's more than the overstay fine, but no mark in the passport which could cause problems in the future.
What is your location? I applied at the London embassy for a 60 day single entry and got it in 2 days it looks daunting to start with, but you can upload everything via a Jpeg , you can also go to an immigration office in Thailand but that'll use up a day and also airlines sometimes ask to see a visa if you are staying over 30 days and can refuse boarding, my advice is do it before you depart. Photo of passport page, photo of yourself passport style, receipt for 1st night stay, screenshot of airline ticket is all you need
Change your local currency at home and take a small amount of Baht (5,000) enough for one night, then the following day you'll get a much more favourable FOREX at your resort or city.